Screen for lamp filament



@et 7, 1969 H, HQRSTER ET AL 3,471,737

SCREEN FOR LAMP FILAMENT Filed May 12. 1967 HoRsT HRsTER IMEMORS JAN cmmmEKAMP AGENT nit-ed States atent O U.S. Cl. 313-240 6 Claims ABSTRACT OF THE DISCLOSURE In an incandescent lamp a screen substantially surrounds the filament, the screen being formed of wire having alternate straight and curved spring sections, whereby tension in the screen wire, even when it is heated during operation of the lamp, is maintained by the spring sections.

The invention relates to an incandescent lamp having a lament and a framework secured to the current-supply wires of said filament and provided with a screen consisting of wire material.

Such a lamp is known; the said screen has for its object to minimize the degree of blackening of the interior of the lamp bulb due to the deposition of evaporated material of the filament. This drawback especially occurs in incandescent lamps having a comparatively heavily loaded tilament, for example, projection lamps or filmstudio lamps.

Applicant has found that it is of importance to protect the elements of the screen as far as possible from sagging during the use of the lamp. FoFr if the distance between these screen-wire elements increases, the degree of blackening of the interior of the lamp bulb also increases. This drawback becomes particularly disturbing if the relevant lamp has comparatively large dimensions, since in this case the distance lbetween the supporting points of the screen-wire elements is comparatively large and moreover the filament is used at a comparatively high temperature.

The object of the present invention is to provide a construction for the screen of such a lamp which on the one hand is simple and on the other hand, as shown by experiments, leads to an embodiment in which the screenwire elements continue to be subjected to a tensile stress also during a longer operation of the lamp.

The incandescent lamp of the aforementioned kind according to the invention is characterized in that the screen consists of wire material stretched out on the framework, substantially straight screen-wire elements alternating with tensile spring elements obtained by a local deformation of the screen-wire material. In this embodiment, the tensile spring elements holding the screen in the prestressed state are constituted by the screen-wire material itself. By a suitable choice .of the areas at which the said tensile spring elements are arranged in the configuration of the screen, it may be achieved that during operation of the lamp the temperature of said tensile spring elements remains so much lower that these elements can prestress the screen.

In a favourable embodiment of an incandescent lamp according to the invention, the tensile spring elements consist of helically wound screen-wire elements.

The invention will now be described more fully with reference to the diagrammatic and perspective drawing, which shows an embodiment of a screen for an incandescent lamp according to the invention. For the sake 0f clarity, the bulb and the cap of the relevant lamp have been omitted. For the same reason, only a few screen wires are shown.

The construction shown has two terminal wires 1 between which a filament 4 is stationed-also with the aid of supporting beams 2 of insulating material and of supporting hooks 3. Furthermore, a framework comprising beams 5 and interposed stay wires 6 is secured to the terminal wires 1. Screen wires 7 are stretched between the said stay wires. The wires 7 consist of straight wire portions 8 alternating with tensile spring elements 9. The elements 9 are obtained by a local deformation of the screenwire material; in the embodiment shown, they consist of helically wound wire portions.

It is ensured by the tensile spring elements 9 that also during a longer operation ofthe lamp comprising the construction shown, the screen wires 7 continue to be subjected to a tensile stress so that the sag of said wires will tbe to a minimum. Especially in the case of lamps having comparatively heavily loaded filaments, this is of great impartance.

What is claimed is:

1. In an incandescent lamp including a pair of spaced current-supply wires and a filament supported between these wires, the improvement in combination therewith, comprising: a framework secured to the current-supply wires and a screen of wire material supported on the framework and substantially surrounding the filament at least on four sides, the screen formed of wire 'having alternate straight sections and tensile-spring sections whereby the screen wire is maintained in tension when assembled and during operation of the lamp.

2. A lamp as defined in claim 1 wherein the screen is formed of a single continuous strand of wire with the tensile-spring sections being helically wound portions thereof.

3. A lamp as defined in claim 1 wherein the currentsupply members are substantially parallel, with the filament in a plane dened therebetween, and the framework has a generally rectangular box-shape comprising two sub-frames, each secured to one current-supply wire and oriented transverse to said plane, with the screen wire circumscribing the sub-frames.

4. A lamp as defined in claim 1 wherein said screen is formed of a single continuous strand of wire with the spring sections being curved portions thereof and being disposed about the framework remotely from the filament, whereby these spring sections will be less heated than the straight sections for supporting the latter from sagging.

5. A method for providing tension in a substantially straight wire wound about a framework and substantially surrounding the filament as a screen in an incandescent lamp, comprising the steps:

y(a) deforming the wire in a plurality of axially spaced positions prior to assembly of the lamp, thereby providing spring sections, and

(b) placing the entire wire including these spring sections in tension about the framework during assembly, the wire then being maintained in tension by the spring sections.

References Cited UNITED STATES PATENTS Quesseque 313-42 Smith 313-240 X Van Horn 313-42 Van Horn 313-240 X Van Horn 313-33 4 Van Horn et al. 313-240 X Woodward et al. 313-315 X Biggs et al. 313-38 |Wiley 313-42 Chaiten 313-38 Van Tijen et al. 313-348 X JOHN W. HUCKERT, Primary Examiner J. R. SHEWMAKER, Assistant Examiner U.S Cl. X.R. 

